as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Example Sentences
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Recent Examples of insidious
The work of documentaries must be rigorous, contextualized, and unflinching enough to help stop the progression of an insidious message and movement.
—
Alison Foreman, IndieWire, 19 Mar. 2026
The show, which runs through March 28, has a blistering message to impart about the insidious nature of authoritarian political movements and the dangers of being oblivious or indifferent.
—Christopher Arnott, Hartford Courant, 18 Mar. 2026
But the kind of harassment that may not rise to the level of a crime in most countries – more pervasive and more subtle, but nonetheless insidious – has largely remained unacknowledged in Brazilian jiu-jitsu.
—Ina Seethaler, The Conversation, 4 Mar. 2026
Moderate beauty, yet insidious.
—Literary Hub, 2 Mar. 2026
See All Example Sentences for insidious
Alison Foreman, IndieWire, 19 Mar. 2026
The show, which runs through March 28, has a blistering message to impart about the insidious nature of authoritarian political movements and the dangers of being oblivious or indifferent.
—Christopher Arnott, Hartford Courant, 18 Mar. 2026
But the kind of harassment that may not rise to the level of a crime in most countries – more pervasive and more subtle, but nonetheless insidious – has largely remained unacknowledged in Brazilian jiu-jitsu.
—Ina Seethaler, The Conversation, 4 Mar. 2026
Moderate beauty, yet insidious.
—Literary Hub, 2 Mar. 2026
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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Greece is one of the main entry points into the European Union for people fleeing conflict and poverty in the Middle East, Africa and Asia, with many making the short but often treacherous journey from the Turkish coast to nearby Greek islands in small boats.—
ABC News,
ABC News,
1 Apr. 2026
-
On the Columbia River and its tributaries, the party had to dig out five new canoes and then paddle them through treacherous rapids.—
Craig Fehrman,
The Conversation,
1 Apr. 2026
Adjective
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One search can yield a long list of options, each with its own rules, conditions, and subtle differences that are easy to miss at first glance.—
Matthew Kayser,
Miami Herald,
8 Apr. 2026
-
However, a slight blurring of stars at the edge of the frame seems to betray the subtle motion of the spacecraft — or camera — over the course of the 10-second exposure.—
Anthony Wood,
Space.com,
8 Apr. 2026
Adjective
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Five of the cases involved hospice care facilities in several cities across Los Angeles County that submitted false claims to Medicare for patients who were not terminally ill and were not eligible for services, prosecutors said.—
Thao Nguyen,
USA Today,
3 Apr. 2026
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This means that precious time was likely lost at the beginning as police investigated a lead that was based on false assumptions.—
Lizzie Lanuza,
StyleCaster,
3 Apr. 2026
Adjective
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In the class action suit, Rodriguez requested a jury trial, damages, restitution and injunctive relief to prevent Hollister from continuing to use its alleged deceptive pricing practices.—
Jennifer Bringle,
Footwear News,
6 Apr. 2026
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Samuel Nana Opoku, a resident of Fairfax County, Virginia, is facing charges of money laundering, felony theft by taking, five counts of identity fraud, and initiation of deceptive commercial email.—
Dan Raby,
CBS News,
2 Apr. 2026
Adjective
-
The government took a genuine invitation to collaborate as a perfidious power grab.—
Gideon Lewis-Kraus,
New Yorker,
14 Mar. 2026
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For those trying to read Iran’s future, the lesson of 1953 is not just that foreign powers can be perfidious.—
Bobby Ghosh,
Time,
5 Mar. 2026
Adjective
-
Google disputes the results and notes that Oumi used the SimpleQA benchmark, an AI test developed by OpenAI that contains incorrect information in its own right.—
Jon Martindale,
PC Magazine,
8 Apr. 2026
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Google spokesperson Ned Adriance tells the Times that Google believes SimpleQA contains incorrect information.—
ArsTechnica,
ArsTechnica,
7 Apr. 2026
Adjective
-
Sometimes that’s totally wrong, because people are overestimating their kids or underestimating Joan Mitchell or whomever.—
Andrew Marantz,
New Yorker,
5 Apr. 2026
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Or show off the Sombor Shuffle with an 11-footer off the wrong foot.—
Troy Renck,
Denver Post,
5 Apr. 2026
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 9 Apr. 2026.
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